- Metal quinolinolate-fullerene(s) donor-acceptor complexes: Evidence for organic LED molecules acting as electron donors in photoinduced electron-transfer reactions
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Tris(quinolinolate)aluminum(III) (AlQ3) is the most widely used molecule in organic light-emitting devices. There exists a strong demand for understanding the photochemical and photophysical events originating from this class of molecules. This paper provides the first report on the electron donor ability of MQn (M = Al or Zn for n = 3 or 2) complexes covalently connected to a well-known electron acceptor, fullerene. To accomplish this, fullerene was functionalized with 8-hydroxyquinoline at different ligand positions and their corresponding zinc(II) and aluminum(III) complexes were formed in situ. The weakly fluorescent metal quinolinolate-fullerene complexes formed a new class of donor-acceptor conjugates. The stoichiometry and structure of the newly formed metal quinolinolate-fullerene complexes were established from various spectroscopic methods including matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and computational density functional theory studies. Electrochemical studies involving free-energy calculations suggested the possibility of photoinduced electron transfer from excited metal-quinolinolate complex to the appended fullerene entity. Femtosecond transient absorption studies confirmed such a claim and analysis of the kinetic data allowed us to establish the different photophysical events in sufficient detail. The novel features of this class of donor-acceptor conjugates include faster charge recombination compared to charge separation and decay of the charge-separated state to populate the low-lying fullerene triplet state in competition with direct charge recombination to the ground state.
- D'Souza, Francis,Maligaspe, Eranda,Zandler, Melvin E.,Subbaiyan, Navaneetha K.,Ohkubo, Kei,Fukuzumi, Shunichi
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- Rational In Silico Design of an Organic Semiconductor with Improved Electron Mobility
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Organic semiconductors find a wide range of applications, such as in organic light emitting diodes, organic solar cells, and organic field effect transistors. One of their most striking disadvantages in comparison to crystalline inorganic semiconductors is their low charge-carrier mobility, which manifests itself in major device constraints such as limited photoactive layer thicknesses. Trial-and-error attempts to increase charge-carrier mobility are impeded by the complex interplay of the molecular and electronic structure of the material with its morphology. Here, the viability of a multiscale simulation approach to rationally design materials with improved electron mobility is demonstrated. Starting from one of the most widely used electron conducting materials (Alq3), novel organic semiconductors with tailored electronic properties are designed for which an improvement of the electron mobility by three orders of magnitude is predicted and experimentally confirmed.
- Friederich, Pascal,Gómez, Verónica,Sprau, Christian,Meded, Velimir,Strunk, Timo,Jenne, Michael,Magri, Andrea,Symalla, Franz,Colsmann, Alexander,Ruben, Mario,Wenzel, Wolfgang
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- Understanding M-ligand bonding and: Mer -/ fac -isomerism in tris(8-hydroxyquinolinate) metallic complexes
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Tris(8-hydroxyquinolinate) metallic complexes, Mq3, are one of the most important classes of organic semiconductor materials. Herein, the nature of the chemical bond in Mq3 complexes and its implications on their molecular properties were investigated by a combined experimental and computational approach. Various Mq3 complexes, resulting from the alteration of the metal and substitution of the 8-hydroxyquinoline ligand in different positions, were prepared. The mer-/fac-isomerism in Mq3 was explored by FTIR and NMR spectroscopy, evidencing that, irrespective of the substituent, mer- and fac-are the most stable molecular configurations of Al(iii) and In(iii) complexes, respectively. The relative M-ligand bond dissociation energies were evaluated experimentally by electrospray ionization tandem mass spectrometry (ESI-MS-MS), showing a non-monotonous variation along the group (Al > In > Ga). The results reveal a strong covalent character in M-ligand bonding, which allows for through-ligand electron delocalization, and explain the preferred molecular structures of Mq3 complexes as resulting from the interplay between bonding and steric factors. The mer-isomer reduces intraligand repulsions, being preferred for smaller metals, while the fac-isomer is favoured for larger metals where stronger covalent M-ligand bonds can be formed due to more extensive through-ligand conjugation mediated by metal d orbitals.
- Lima, Carlos F.R.A.C.,Taveira, Ricardo J. S.,Costa, José C. S.,Fernandes, Ana M.,Melo, André,Silva, Artur M. S.,Santos, Luís M.N.B.F.
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p. 16555 - 16565
(2016/07/06)
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- Hot melt reaction preparation of luminescent material 8-hydroxy quinoline aluminum method
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The invention discloses a method for preparing a luminescent material aluminum 8-hydroxyquinolinate through hot melting reaction. Pure aluminum 8-hydroxyquinolinate is directly prepared by using 8-hydroxyquinoline and anhydrous aluminum chloride as reaction raw materials and using a hot melting method. The method concretely comprises the following steps of alternately adding the reaction raw materials, namely 8-hydroxyquinoline and anhydrous aluminum chloride into a reactor according to the molar ratio of 3:1, heating to 80-100 DEG C, and reacting for 2-4h; and after ending the reaction, cooling to the room temperature, and discharging to obtain aluminum 8-hydroxyquinolinate with the purity of 97-99%. The method has the advantages of short process, high product yield, no waste liquid discharge and low production cost and is environmental friendly.
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Paragraph 0010-0012
(2017/03/17)
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- A theoretical and experimental study on meridional-facial isomerization of tris(quinolin-8-olate)aluminum (Alq3)
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The rationale behind the stereospecific synthesis of a facial isomer of tris(quinolin-8-olate)aluminum (Alq3) is studied by density functional theory (DFT) calculations, which predict the favourable influence of an H3O+ ion on the distribution ratio between a meridional and a thermodynamically unstable facial isomer. This journal is the Partner Organisations 2014.
- Iwakura,Ebina,Komori-Orisaku,Koide
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p. 12824 - 12827
(2014/08/18)
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- The effect of electron donating and withdrawing groups on the morphology and optical properties of Alq3
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By adding electron donating (EDG) and withdrawing groups (EWG) to the Tris-(8-hydroxyquinoline) aluminum (Alq3) molecule, the emission color can be tuned. In this study the effect of EDG and EWG on the morphology and optical properties of Alq3 were investigated. Alq3 powders was synthesized with an EDG (-CH3) substituted at positions 5 and 7 ((5,7-dimethyl-8-hydroxyquinoline) aluminum) and EWG (-Cl) at position 5 ((5-chloro-8-hydroxyquinoline) aluminum). A broad absorption band at ~380 nm was observed for Alq3. The bands of the substituted samples were red-shifted. The un-substituted Alq3 showed a high intensity emission peak at 500 nm. The -Cl and -CH3 samples showed a red-shift of 33 and 56 nm respectively. The morphology of the samples was studied using a scanning electron microscope. The photo degradation of the samples was also investigated and the dimethyl sample shows the least degradation to the UV irradiation over the 24 h of continuous irradiation.
- Duvenhage,Visser,Ntwaeaborwa,Swart
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- Synthesis of nano-pore size Al(III)-imprinted polymer for the extraction and preconcentration of aluminum ions
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In this study, an ion imprinted polymer (IIP) was prepared for the selective separation and preconcentration of trace levels of aluminum. Al(III) IIP was synthesized in the presence of Al(III)-8-hydroxyquinoline (oxine) complex using styrene and ethylene glycol dimethacrylate as a monomer and crosslinker, respectively. The imprinted Al(III) ions were completely removed by leaching the IIP with HCl (50 % v/v) and were characterized by FTIR and scanning electron microscopy. The maximum sorption capacity for Al(III) ions was found to be 3.1 mg g-1 at pH 6.0. Variables affecting the IIP solid phase extraction were optimized by the univariable method. Under the optimized conditions, a sample volume of 400 mL resulted in an enhancement factor of 194. The detection limit (defined as 3 S b/m) was found to be 1.6 μg L-1. The method was successfully applied to the determination of aluminum in natural water, fruit juice and cow milk samples.
- Shakerian, Farid,Dadfarnia, Shayessteh,Shabani, Ali Mohammad Haji
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p. 669 - 676
(2013/07/27)
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- DOPED ALUMINUM OXIDES
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A process of preparing a doped aluminum oxide, includes providing a solution comprising 8-hydroxyquinoline; an aluminum precursor; a dopant precursor, and a reaction solvent; isolating a precipitate from the solution; and calcining the precipitate to form the doped aluminum oxide. Compositions may be prepared which include tris (8- hydroxyquinolinato) aluminum and (8-hydroxyquinolinato) z M, wherein M is a metal ion and the value of z is equivalent to the oxidation state of the metal ion.
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Page/Page column 9
(2012/09/10)
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- Method for Preparation Metal Compounds of 8-Hydroxyquinoline or Derivatives
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This invention, which involves “the preparation method of 8-hydroxyquinoline metallic compound”, is a synthetic method of organic electroluminescent materials. The preparation method of compound Mqnqm′ is to add solution prepared by Zengshui solvent and industrial ligand into reaction vessel, stir it at a certain temperature, and then achieve high-purity product, as for the Mqnqm′, M stands for Al, Li, n stands for 1-3, m is 0-2, q is 8-hydroxyquinoline and its derivatives, and q′ is ligand different from q. Zengshui solvent is adopted in this invention which can react effectively and thus reducing reaction time and avoiding cumbersome operation and the refining process; this invention also increases total yield and purity, the mother liquor obtained can be recycled, which reduces environment pollution and cost as well. This technology can also spread to the preparation of other 8-hydroxyquinoline metallic compound and the product achieved can be used as electroluminescent materials or electron-transport materials.
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Page/Page column 2
(2012/06/01)
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- Highly selective and sensitive fluorescent paper sensor for nitroaromatic explosive detection
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Rapid, sensitive, and selective detection of explosives such as 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (TNP), especially using a facile paper sensor, is in high demand for homeland security and public safety. Although many strategies have been successfully developed for the detection of TNT, it is not easy to differentiate the influence from TNP. Also, few methods were demonstrated for the selective detection of TNP. In this work, via a facile and versatile method, 8-hydroxyquinoline aluminum (Alq3)-based bluish green fluorescent composite nanospheres were successfully synthesized through self-assembly under vigorous stirring and ultrasonic treatment. These polymer-coated nanocomposites are not only water-stable but also highly luminescent. Based on the dramatic and selective fluorescence quenching of the nanocomposites via adding TNP into the aqueous solution, a sensitive and robust platform was developed for visual detection of TNP in the mixture of nitroaromatics including TNT, 2,4-dinitrotoluene (DNT), and nitrobenzene (NB). Meanwhile, the fluorescence intensity is proportional to the concentration of TNP in the range of 0.05-7.0 μg/mL with the 3σ limit of detection of 32.3 ng/mL. By handwriting or finger printing with TNP solution as ink on the filter paper soaked with the fluorescent nanocomposites, the bluish green fluorescence was instantly and dramatically quenched and the dark patterns were left on the paper. Therefore, a convenient and rapid paper sensor for TNP-selective detection was fabricated.
- Ma, Yingxin,Li, Hao,Peng, Shan,Wang, Leyu
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p. 8415 - 8421
(2013/01/15)
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- Surfactant-assisted hydrothermal route to organometallic tris(8-hydroxyquinoline)aluminum nanorod bundles
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A new surfactant-assisted hydrothermal route was presented to prepare organometallic tris(8-hydroxyquinoline)aluminum nanorod bundles on a large scale. In this hydrothermal system, sodium dodecylbenzenesulfonate (Chemical formula: C12H25-C6H4-SO 3Na, SDBS) played key roles in controlling the morphology and quality of the resultant products. The as-prepared nanorod bundles showed enhanced PL emission compared to submicron particles prepared by the same hydrothermal method. Copyright
- Ma, Dekun,Zhang, Junhao,Hu, Xiaokai,Zhou, Hongyang,Qian, Yitai
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p. 630 - 631
(2008/02/07)
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- Synthesis of reactive [Al(Et)(q′)2] (q′ = 2-methyl-8-quinolinolato) serving as a precursor of light emitting aluminum complexes: Reactivity, optical properties, and fluxional behavior of the aluminum complexes
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Reaction of AlEt3 with 2-methyl-8-quinolinol gave ethylbis(2-methyl-8-quinolinolato)aluminum complex [Al(Et)(q′)2] 1. The complex 1 provided photoluminescent Al complexes by reactions with phenols, carboxylic acid, and H2O. The α-CH2 hydrogens in the Et group of 1 was diastereotropic as revealed by 1H NMR spectroscopy because of the presence of a chiral center at Al. The chirality at Al was dynamically lost at elevated temperature in CDCl2CDCl2 and DMSO-d6, as indicated by temperature dependent 1H NMR spectroscopy. This dynamic or fluxional behavior of 1 is explained by rotation of the 2-methyl-8-quinolinolato ligand. The kinetic parameters of the dynamic process were estimated at ΔH?? = 135 kJ mol-1 and ΔS? = 159 J K-1 mol-1 in CDCl2CDCl2 and at ΔH? = 124 kJ mol-1 and ΔS? = 151 J K-1 mol-1 in DMSO-d6, respectively, at 350 K. Structures of some of the obtained Al complexes were confirmed by single-crystal X-ray crystallography. These Al complexes showed photoluminescence peaks at 492-507 nm in CHCl3 with quantum yields of 7-23%.
- Iijima, Takayuki,Yamamoto, Takakazu
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p. 5016 - 5023
(2007/10/03)
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- PROCESS TO MAKE METAL COMPLEXES WITH VOLATILE LIQUID METAL COMPOUNDS
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Processes for making metal complexes that are useful in organic light emitting devices M (OLEDs) involve reacting a volatile liquid metal compound with a compound that has at least one hydroxyl (OH) group, such as 8-hydroxyquinoline. Exemplary volatile liquid metal compounds include trimethylaluminum, triethylaluminum, triisobutylaluminum, diisobutylaluminum hydride, dimethylaluminum chloride, and diethylaluminum chloride. One useful metal complex that can be produced is tris(8-hydroxyquinoline)aluminum (Alq3).
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Page/Page column 9-11
(2008/06/13)
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- Improvement on the photorefractive performance of a monolithic molecular material by introducing electron traps
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The ehancement in photorefractive performance was observed by introducing tris(8-hydroxyquinoline) aluminum (Alq3) as electron traps. A small amount of Alq3 formed quantum dots in (9-ethyl-9H-carbazol-3- ethylmetjylent)(4-nitrophenyl)-amine (ECYENPA), serving as electron traps. Alq3 prevented the the electron-hoe recombination and accelerate the electron-hole separation, benefiting the buildup of internal space-charge electric field. The analysis show that for a sample doped with 2 wt% of Alq 3 produced large two-beam coupling coefficient of 424 cm-1 in contrast to a value of 232 cm-1 for a sample without Alq 3.
- Zhang, Jie,Chen, Zhijian,Liu, Yihong,Huang, Maomao,Wei, Qun,Gong, Qihuang
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p. 1323 - 1325
(2008/10/09)
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- Synthesis and reactivity of A1(Et)q2′ (q′ = 2-methyl-8-quinolinolato) and crystal structures of [A1(Et)2q]2 and A1q′2q (q = 8-quinolinolato)
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A crystal structure of a dimeric aluminum complex ([Al(Et)2(q)]2, q = 8-quinolinolato) (1) obtained by reaction of A1Et3 with 8-quinolinol has been determined by X-ray crystallography. Reaction of AlEt3 with 2-methyl-8-quinolinol gave a new reactive complex (Al(Et)q′2] (q′ = 2-methyl-8-qinolinolato) (2)) in good yield. Reaction of 2 with 8-quinolinol provided Alq′2q (3) and the crystal structure of 3 was determined.
- Yamaguchi, Isao,Iijima, Takayuki,Yamamoto, Takakazu
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p. 229 - 232
(2007/10/03)
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- Method of making metal 8-quinolinolato complexes
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A method for making metal (8-quinolinolate) complexes from air and moisture stable reagents is described. For example, the making of aluminum tris(quinolinolates), such as tris(8-hydroxyquinolinato), from aluminum (III) carboxylates, such as aluminum lactate and aluminum stearate, is described. Examples of bis and tris metal (8-quinolinolates) as well as single and mixed ligand complexes are given.
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- Effects of systematic methyl substitution of metal (III) tris(n-methyl-8-quinolinolato) chelates on material properties for optimum electroluminescence device performance
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We relate the chemical structure of a series of methyl (Me) substituted group III metal tris(8-quinolinolato) chelates (nMeq3M: n = 0, 3, 4, 5; M = Al3+, Ga3+) to their photoluminescence (PL), electroluminescence, and thermal properties. Methylation of the 8-quinolinol ligand at the 3 or 4 position (pyridyl ring) results in a factor of 1.4 and 3.0 enhancement of PL quantum efficiency (OPL), respectively, whereas methylation at the 5 position (phenoxide ring) results in a factor of ~ 3.0 decrease in PL relative to the unsubstituted analogue. Electroluminescent quantum efficiencies of undoped organic light-emitting devices using the aluminum tris(8-quinolinolato) chelates are 1, 0.45, 1.4, and 0.80% for unsubstituted 5-, 4-, and 3-methyl-8-quinolinol ligands, respectively. Devices made with the latter two ligands have a higher operating voltage to generate the same current density. Similar trends were observed for methylation of gallium tris(8-quinolinolato) chelates. We relate these results to the thermal properties of the compounds measured by simultaneous differential scanning calorimetry and thermal gravimetric analysis. The C-4 methylated derivatives exhibit ~60 °C lower crystalline melting points than all other derivatives, indicating the weakest cohesive forces between molecules. Unlike Alq3, both the C-4 and C-5 methylated derivatives show no recrystallization of the glassy state below 500 °C and exhibit ~-20-25 °C higher glass transition temperatures. We infer that methylation of the 8-quinolinol ligand reduces intermolecular interactions and consequently impedes charge transport through the film.
- Sapochak,Padmaperuma,Washton,Endrino,Schmett,Marshall,Fogarty,Burrows,Forrest
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p. 6300 - 6307
(2007/10/03)
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- Solid state preparation of the (8-hydroxyquinolinato)aluminum(III) complex from aluminum isopropoxide and 8-hydroxyquinoline
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A new alternate method is described for the preparation of the (8-hydroxyquinolinato)aluminum(III) complex in the solid state from aluminum isopropoxide. The complex was characterised by IR spectra, elemental analyses and X-ray spectroscopy using a compact X-ray diffraction analyser. The light yellow complex prepared in the solid state has an identical structure with the one prepared by the wet method.
- Saxena
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p. 1747 - 1767
(2008/10/09)
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